Karabiner setting, for Kensington Trackball

kensington-trackball.json

{
  "title": "for Kensington Trackball",
  "rules": [
    {
      "description": "L_btn + R_btn to Button 2",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "simultaneous": [
              {
                "pointing_button": "button1"
              },
              {
                "pointing_button": "button2"
              }
            ],
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "pointing_button": "button2"
            }
          ]
        }
      ]
    },
    {
      "description": "R_btn to Button 3, and R_btn + mouse motion to scroll wheel",
      "manipulators": [
        {
          "type": "basic",
          "from": {
            "pointing_button": "button2",
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "to": [
            {
              "set_variable": {
                "name": "flg_scrolling",
                "value": 1
              }
            }
          ],
          "to_after_key_up": [
            {
              "set_variable": {
                "name": "flg_scrolling",
                "value": 0
              }
            }
          ],
          "to_if_alone": [
            { 
              "pointing_button": "button3"
            }
          ]
        },
        {
          "type": "mouse_motion_to_scroll",
          "from": {
            "modifiers": {
              "optional": [
                "any"
              ]
            }
          },
          "conditions": [
            {
              "type": "variable_if",
              "name": "flg_scrolling",
              "value": 1
            }
          ]
        }
      ]
    }
  ]
}